I see that a lot of other people are having trouble doing this combo reliably on pad too so I’ll share what worked for me.
Go to button config and set L2/Left Trigger to focus attack instead of lk+mk+hk. As ryu, the only move (that I’m aware of) that takes advantage of lk+mk+hk is ex-tatsu which can just as easily be done in the regular way.
You can also press forward+focus, forward, to dash instead of focus, forward, forward.
So instead of having to be a thumb-rockstar pressing square, triangle+circle, forward, forward, ultra, you can just press square, forward+L2, forward, ultra.
On xbox, X, Y+B, forward, forward, ultra…turns into X, forward+LeftTrigger, forward, ultra.
Using this I went from not being able to do this combo at all to doing it too fast and having to slow the ultra input down so that it doesn’t just hit once and then pass underneath.
Hope this helps you guys.